No pattern found in Northern Hemisphere atmospheric blocking and weather extremes

A new paper in press at GRL (Barnes et al 2014) suggests that the idea of “blocking” patterns being on the increase due to climate change factors such as sea ice have no statistically significant component. As readers may know, such blocks are blamed for causing things like the Russian Heat Wave of 2010, which has been shown to be due to natural variability. The authors report “No clear hemispheric increase in blocking is found for any blocking index…”.

They go on to say that “…an increase in blocking could mean an increase in weather extremes as Arctic sea ice continues to decline. However, both observational and modeling studies suggest that any potential link between sea ice and midlatitude weather may be masked by internal variability.” and, “…the link between recent Arctic warming and increased Northern Hemisphere blocking is currently not supported by observations.”.

Exploring recent trends in Northern Hemisphere blocking

Abstract
Observed blocking trends are diagnosed to test the hypothesis that recent Arctic warming and sea ice loss has increased the likelihood of blocking over the Northern Hemisphere.

To ensure robust results, we diagnose blocking using three unique blocking identification
methods from the literature, each applied to four different reanalyses. No clear hemispheric increase in blocking is found for any blocking index, and while seasonal increases and decreases are found for specific isolated regions and time periods, there is no instance where all three methods agree on a significant trend. Blocking is shown to exhibit large interannual and decadal variability, highlighting the difficulty in separating any potentially forced response from natural variability.

Introduction

Over the past two decades, the Arctic has experienced unprecedented sea ice loss [NSIDC, 2013]. Recent studies suggest that the recent decline in sea ice has led to an increase in blocking over North America and Europe in all seasons but spring [e.g. Liu et al., 2012; Francis and Vavrus, 2012] due to a slow-down of the large-scale flow in response to the reduced lower-tropospheric temperature gradient. Blocking is strongly tied to weather extremes in the midlatitudes (e.g. cold snaps, heat waves), and can persist for days to weeks [e.g. Black et al., 2004; Dole et al., 2011], so an increase in blocking could mean an increase in weather extremes as Arctic sea ice continues to decline. However, both observational and modeling studies suggest that any potential link between sea ice and midlatitude weather may be masked by internal variability [e.g. Barnes, 2013; Screen et al., 2013]. Here, we address whether robust trends in blocking have been observed over the past few decades in response to the hypothesis that recent Arctic sea ice loss has increased the likelihood of blocking over the Northern Hemisphere.

While a handful of previous studies have published trends in blocking [e.g. Barnes, 2013; Croci-Maspoli et al., 2007], there is concern over whether the results are sensitive to the specific blocking detection algorithm employed, the data set used, or the season and time period over which the trend is defined. For this reason, we analyze blocking occurrence with three different detection methods, four different reanalyses, over all four seasons and three different year ranges. Our goal is to quantify whether blocking frequencies have in-fact changed over the satellite era in an effort to (1) advance the discussion of the effects of Arctic change on midlatitude weather and (2) evaluate whether trends in blocking have been observed, regardless of the sea ice hypothesis, e.g., associated with the Atlantic Meridional Overturning circulation, or global temperature increases.

…

Figure 1. Climatological seasonal blocking frequency for the three indices using the MERRA reanalysis from 1980-2012. Red (blue) boxes denote regions where robust increases (decreases) in blocking frequency are found over the 1990-2012 period, as shown in Fig. 2b.

Conclusions

Recent studies have suggested that Arctic warming and sea ice loss over the past 15 years has led to an increase in the occurrence of blocking over the Northern Hemisphere [e.g. Liu et al., 2012; Francis and Vavrus, 2012; Tang et al., 2013]. We address whether blocking frequencies have exhibited robust trends in recent decades by applying three different blocking identification methods to four different reanalyses. No clear hemispheric increase in blocking is evident in any season for any blocking index, although robust seasonal increases and decreases are found for isolated regions. Compositing winter blocking frequencies on high and low September sea ice years yields opposite signed differences depending on the years analyzed, while summer blocking yields positive differences over the North Atlantic and negative over the North Pacific. We strongly caution, however, that these composite differences can be explained by many different dynamical mechanisms, and should not be simply viewed as evidence of the response of blocking to sea ice loss.

These conclusions support those of Barnes [2013], namely, that the link between recent Arctic warming and increased Northern Hemisphere blocking is currently not supported by observations. While Arctic sea ice experienced unprecedented losses in recent years, blocking frequencies in these years do not appear exceptional, falling well within their historically observed range. The large variability of blocking occurrence, on both inter-annual and decadal time scales, underscores the difficulty in separating any potentially forced response from natural variability.

Considering that events like Sudden Stratospheric Warmings create blocking in the winter is a fairly steady event, (occurs every other year statistically, major ones, that is) It is obvious this study would come to the same conclusion there is no increase in blocking.

Not sure I understand or even like the term blocking. Is the main driver not the Jet Stream which is becoming increasingly active and meandering, and when it gets stuck in a single position, “the weather”, which may be extreme owing to large meanders, may repeat for days to weeks?

Off topic, but my main post on Energy Matters this week contrasts energy production in Europe with N America – may be of interest to some.

“While arctic sea ice experienced unprecedented losses in recent years …… .”
Unprecedented?
Says who?
There are plenty of reports at Greenwich, The Admiralty and elsewhere from fishermen, whalers, sealers and the like, going back a couple of hundred years or more, that talk of far less sea ice than there has been recently.
Not to mention the trees that grew in Greenland as reported here recently.

Expect a paper out soon saying that co2 hasn’t mad the polar vortex wilder. It’s always the same old story: extreme weather / climate claims are made, sceptics say woah! A paper later comes out from Warmists flattening such claims. Same with extinctions. Remember the bees, frogs, lizards etc.

For the authors to reference “unprecedented ice loss” seems nonsensical given that the record only really got going in 1979. Apart from that it is nice to see them conclude that what is happening vis-a-vis blocking seems to be entirely natural.

“Researchers expected the topography data to reveal volcanic features on Venus but they were surprised to learn that at least 90% of the planet’s surface was covered by lava flows and broad shield volcanoes”

I am guessing this heat from lava flows is around 600+ degrees , what effect would this have on the atmosphere.

The term “unprecedented ice loss” is simply inaccurate.
It was sufficient of them to note “lowest in the last 30 years” to be truthful.
We all saw the images of the US subs emerge to the surface in the North Pole in open water on May.
There are also multiple evidence of the Arctic being ice free on summertime in the past.

For those commenting on unprecedented Arctic sea ice loss I recently came across a paper suggesting that Arctic sea ice was low during the LIA. Hated the idea at first but have warmed to it. But difficult to reconcile with other data sources.

The pronounced decrease in ice cover observed in both our terrestrial and oceanic proxy-based reconstructions between the late fifteenth and early seventeenth centuries occurred during the widespread cooling period known as the Little Ice Age (about AD 1450–1850 (ref. 18)).

As usual the body checking blockers of the Hockey Team don’t have their eyes on the puck. If anything, blocking should be analyzed for impacts on ending interglacials. Looks at the impacts of a stationary Hudson Bay low on accumulation on the Canadian Shield.

What interesting about melting ice and a warming Arctic is that it decreases the temperature contrast between the high latitudes and low latitudes.
This of course LOWERS the potential energy in the system for many powerful weather systems and the amount of meridional flow needed to balance the heat differential.

If our planet were heated equally, for instance or if the heating remained at the same uneven levels year round, then we would have a much easier to evaluate but still complex atmosphere, ocean, land and sun interaction.

However, throw in the earths spinning, revolving around the sun, magnetic fields, increases in CO2, volcanic activity and so on and you have a constantly changing system that nobody grounded to reality can predict 50 years from now……or apparently even for 10 years out with much skill.

It’s not possible to accurately represent the physics with all the right mathematical equations and use that to predict the future.

It is making more sense to just look at a combination of cycles like the Oceanic PDO or AMO and see how the system responded. Pattern recognition of the atmospheric response studying the past does not require knowledge of all the physics as the response is in fact from everything in the system, including unknowns.

We should give that MUCH greater weight until we figure out what it is exactly that caused those patterns.

For those commenting on unprecedented Arctic sea ice loss I recently came across a paper suggesting that Arctic sea ice was low during the LIA. Hated the idea at first but have warmed to it. But difficult to reconcile with other data sources.

There are physical (geometric – such as latitude of the sea ice in the Antarctic and Arctic => solar elevation angles through the day and night, and air mass thickness at each SEA) and geological – results (sea ice albedo changes through the year, latitude of the sea ice up north and down south) reasons for that effect.

True, they are not “intuitive” in that the CAGW community’s dogma holds that “hotter air temperatures means less ice, less ice forces hotter temperatures” but that is NOT true for today’s current Arctic conditions.

And, by extension, it means that the same thermodynamic equations and geometry will hold true for the Arctic during the Little Ice Age. Less ice in the Arctic (under today’s conditions between August, September, and October) means a cooler earth, more ice in the Antarctic at any time of year (under today’s conditions) means a cooler planet.

“Less ice in the Arctic (under today’s conditions between August, September, and October) means a cooler earth, more ice in the Antarctic at any time of year (under today’s conditions) means a cooler planet.”

Seems plausible. If the polar vortex becomes unstable more polar air will be exported southward and replaced by presumably warmer air. This will come about if the stratosphere cools due to less ozone production and the temperature inversion above the poles disappears. The result will be that the earth becomes a more efficient radiator and cooler, as you say.

I’ve just had a quick look at the paper. A search shows the following:

Keyword / total instances found:

blocking / 161
sun / 0
solar / 0
Lockwood / 0

Now if you look at Barnes’ Figure 4, notice the red line in the top LHS graph…every single peak in the red line corresponds to the minimum at the end of the last 6 solar cycles. And recall that Lockwood linked the 2010 UK winter blocking to low solar activity in my first link, ie “DJF” as it says on Barnes’ graph.

Someone is avoiding bumping to the big solar elephant in their room methinks.

Columbia River (Washington/Oregon) froze in 1916, 1930 and 1949. Not to mention the Willamette River got frozen over in 1924 where a car drove across it for the first time in record history (or so they believed).

I concur on the primacy of observations. There’s far too much darkly underhanded thought-policing being used to herd the climate blog readership towards a politically convenient narrative. It isn’t helpful.